Gog

This is a totally different supervillain that the previous one. Until now, there have been three different versions of this villain, each one more awesome than the other (of course, us being subjective at this moment). Thus, Gog's main attribute seems that he is able to steal the superpowers of superheroes. In this way, he is one of the supervillains who haven't just defeated Superman "“ he literally killed countless of versions of the superhero, in countless different timelines.

The source of his power is debatable, depending on the incarnation we are talking about. In any way, when Doomsday leads an army against an ultimate threat in order to defend Superman, you know you have found one of the most powerful and interesting supervillains.

And he cannot be that easily killed "“ he or she who does the deed must be careful when doing it. And that is because Gog's death would bring the destruction of the Earth. So he needs to be beheaded and have his still living head placed into the Source Wall for all eternity.

So whether he is a god, whether he is a survivor of Imperiex's attack, whether he is just a human survivor of a nuclear accident in Kansas, Gog is definitely a must on this list.